A chain with anti-backbend properties on the first and second sides is known from DE 10 2005 099 154 A1. In the case of this anti-backbend push chain for power transmission in a chain drive, the chain elements are pivoted radially inwards on a chain drive wheel. The hinge openings of the chain link plates are implemented as elongate holes and have a certain amount of play relative to the hinge pins, so that the effective chain pitch in the push strand is reduced. In addition, the ends of the hinge pins have rollers provided thereon, which guide the anti-backbend chain in a separate roller rail guide in the push strand. The hinge openings configured as elongate holes additionally allow a reliable contact of the stiffening contours formed on the end faces of the chain link plates in the push strand.
DE 1 450 699 C1 discloses a further anti-backbend chain. The outer link plates of the outer chain links and the inner link plates of the inner chain links have provided between them stiffening link plates, which are each arranged on a hinge pin and provided with a projection protruding in a direction of chain travel, the end faces of said projection being configured as support surfaces. One end face is configured as a protrusion and the other end face as a recess. The protruding and recessed end faces of the stiffening link plates stiffen the chain in a first pivot direction, whereas the chain remains flexible in the other, second pivot direction. Therefore, this chain runs in a push strand in a guide means so as to prevent, for power transmission through this anti-backbend chain, bending of the chain in the second pivot direction.
The prior art comprises a plurality of additional, very different structural designs of anti-backbend chains. Reference DE 1 180 318 B, for example, shows an anti-backbend chain drive with alternate inner and outer chain links, the contour of the chain link plates being provided with an end face-side stiffening means and the chain being guided between the chain link plates in a guide channel in a push strand. DE 2001 002 310 U1 discloses an anti-backbend chain with identical fork-shaped chain links provided with interengaging stiffening contours on their rear sides. In addition, EP 1 744 079 A1 discloses a chain with anti-backbend properties on the first and second sides, in the case of which the end faces of the chain link plates have complementary stiffening contours, at least one hinge opening being configured as an elongate hole so as to allow in the push strand a reliable interengagement of the end face-side stiffening contours by means of a reduced chain pitch.
Reference DE 1 046 422 B1 discloses a further anti-backbend plate link chain comprising a locking mechanism, which prevents the chain links from being pivoted relative to one another and which is disengaged by means of a lateral guide during deflection. A further locking mechanism of an anti-backbend chain is shown in DE 20 2007 002 767 U1, where an arresting element, which is pivotable transversely to the direction of chain travel, is disengaged by means of a guide rail.
The anti-backbend chains and chain drives known in the prior art make use of very different concepts and constructions so as to guarantee stiffening of the chain in the push strand and allow simultaneously deflection of the chain around a chain drive wheel. Many of the known anti-backbend chains are joined by additional measures after stiffening behind the chain drive wheel in the push strand or the chains are locked by means of arresting mechanisms in the second or in both pivot directions. Although many of the anti-backbend chains which have hitherto been used in the prior art proved to be very useful, the mechanisms used are partly complex stiffening and/or locking mechanisms as well as intricate constructions that often require additional space.
JP H07 172786 A deals with a lift chain for a forklift truck whose chain links can be biased relative to one another by means of a leg spring. Every second hinge pin has attached thereto such a leg spring, the two legs of said spring resting on the respective neighboring pin. The chain is therefore always forced back from a stretched position to the folded position.
US 2009/124445 A1 discloses a toothed chain comprising wire spring elements between the chain links. These wire spring elements are intended to make the chain resistant to bending.
GB 12985 A discloses a roller chain. Some of the chain links have upwardly protruding projections having a leaf spring element arranged thereon, which imparts to the chain a certain degree of spring elasticity.